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I have the network topology:

enter image description here

in this topology, in my router, I set the DHCP relay:

admin@MX-RE0# show forwarding-options dhcp-relay
server-group {
    smart_group {
        103.57.xxx.19;
    }
}
group SMART_GROUP {
    active-server-group smart_group;
    interface ae16.0;
    interface ae16.172;   //  this is SVI 103.57.xxx.22/29
    interface ae16.106;   //  this is SVI 45.117.yyy.6/29

...

You see my dhcp relay, I have added the SVI ae16.172 and ae16.106. But however, when I boot the DHCP Client host, it can not find the DHCP proxy.

enter image description here

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If I set the DHCP pool's IP section under vlan 172, the DHCP client can rquest DHCP IP success.

So, there have issue for DHCP relay in different vlans.

How to solve this issue? is my dhcp-relay config any problem?

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The gateway device is Juniper MX480.

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EDIT-01

When I show dhcp relay statistics:

enter image description here

  • One thing is that you do not put in a DHCP relay for the VLAN on which the DHCP server is connected, only for the VLANs to which the DHCP server is remote. As far as I can tell, you should only have a DHCP relay on interface ae16.106 for VLAN 106. The VLAN to which the DHCP server is connected should not have a relay because devices on that VLAN can contact the server directly. – Ron Maupin Dec 18 '19 at 16:21
  • I have did like your saying, but the issue is not in there. – 244boy Dec 18 '19 at 17:19
  • Is there any access lists applied to these interfaces? If yes, check that the allow DHCP traffic. – Andrey Prokhorov Dec 19 '19 at 6:48
  • This smells like a routing issue to me. The Network for Vlan106 is probably not known on the site where the DHCP Server resides. You would only need to add the Client facing LAN interface (SVI 45.117.yyy.6/29) to the DHCP relay configuration. – Mario Jost Dec 23 '19 at 15:06

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